The present invention relates to a terminal device, a positioning method, and a recording medium.
A positioning system has been used in practice which locates the present position of a GPS receiver utilizing a satellite navigation system using positioning satellites, such as a global positioning system (GPS). The GPS receiver determines the signal frequency (reception signal frequency) of the signal received from the GPS satellite based on GPS satellite orbital information and the like stored in advance, and achieves synchronization with the reception signal frequency using synchronization means included in the GPS receiver to receive the signal from the GPS satellite.
However, since the frequency of a crystal oscillator or the like which generates a reference clock signal for the synchronization means of the GPS receiver changes depending on the temperature (hereinafter called “drift”), the GPS receiver cannot promptly achieve synchronization with the reception signal frequency when no measures are taken, whereby the positioning time is increased.
In order to deal with this problem, technology has been proposed which determines the drift of the GPS receiver by acquiring one positioning satellite as the first acquisition target using all synchronization means and then acquires the positioning satellites necessary for positioning (JP-A-2005-326281).
However, the above technology has a problem in which the period of time required to acquire the positioning satellites necessary for positioning using the calculated drift may be increased depending on the accuracy of the drift. This makes it difficult to sufficiently reduce the period of time required to calculate the located position.